Method and apparatus for controlling air pollution caused by volatile emissions from storage tanks and the like

ABSTRACT

Method and apparatus for controlling air pollution caused by volatile emissions from petroleum storage tanks and the like, wherein such volatile emissions or vapors are passed through a brine or glycol solution having a controlled temperature range for separating petroleum hydrocarbons, water and air and for collecting the hydrocarbons so that they do not escape to the environment.

United States Patent 1191 Parker, Sr. Dec. 18, 1973 METHOD AND APPARATUSFOR 3,403,522 10/1968 Henry 55/31 CONTROLLING AIR POLLUTION CAUSEDialzarewn u rey BY VOLATILE EMISSIONS FROM 3,648,436 3/1972 Schonewardet a]. 55/88 STORAGE TANKS AND THE LIKE Inventor: George Parker, Sr.,Corpus Christi,

Tex.

Assignees: J. B. Trimble; Dwain Smith,

both of Houston, Tex.; part interest 92911 Filed: Aug. 10, 1972 Appl.No.: 279,499

Primary Examiner-Charles N. Hart Att0rneyPravel, Wilson & Matthews [57]ABSTRACT Method and apparatus for controlling air pollution caused byvolatile emissions from petroleum storage tanks and the like, whereinsuch volatile emissions Or vapors are passed through a brine or glycolsolution having a controlled temperature range for separating petroleumhydrocarbons, water and air and for collecting the hydrocarbons so thatthey do not escape to the environment.

8 Claims, 3 Drawing Figures METHOD AND APPARATUS FOR CONTROLLING AIRPOLLUTIONCAUSED BY VOLATILE EMISSIONS FROM STORAGE TANKS AND THE LIKEBACKGROUND OF THE INVENTION The field of this invention is methods andapparatus for controlling air pollution due to petroleum vapor emissionsfrom storage tanks and the like.

In the storage of petroleum in large storage tanks, vapors are expelleddue to changing temperatures of the atmosphere surrounding the storagetanks and the vapors are also displaced when the tank is filled. In thepast, it has been customary to provide a floating roof in each storagetank so that the amount of vapors were reduced. Such floating roofconstruction has been very expensive, and with older tanks, suchconstruction has been generally impossible since they are usually out ofround and/or they have steel framing which interferes with an adequateseal between the floating roof and the side wall of the tank.

In other instances, vapor recovery has been effected from storage tanksby passing the hydrocarbon vapors through a carbon bed, thenregenerating the bed and cooling it down for re-use. Such vapor recoverysystem is also very expensive and as a consequence is not usedextensively. Refrigeration heat exchange has also been employed forvapor recovery, but it suffers from the disadvantage that the waterwhich is usually present with the hydrocarbon vapors freezes in the heatexchanger tubes, causing heat transfer and flow problems.

Examples of prior art known to applicant are U. S. Pat. Nos. 2,077,019;2,753,691; 2,885,109; 2,889,013; 2,929,463; 3,124,937; 3,581,782;3,648,436; and 3,661,366, and British Pat. No. 893,642, most of whichhave only limited relevancy, if any. The Schlict US. Pat. No. 2,077,019discloses the use ofa brine for controlling the back pressure inapetroleum storage tank, but there is no control of the temperature ofthe brine, and further, such system is dangerous in that if water ispresent in the vapors passing through the pipe in the brine, and thebrine is at or below freezing, ice may form in the pipe and plug off theflow, thus exposing the system to an explosion as the pressures develop.

SUMMARY OF THE INVENTION The present invention relates to methods andapparatus for controlling air pollution caused by volatile emissionsfrom petroleum storage tanks and the like. The present system overcomesthe problems of the prior art and is far less costly. The system of thisinvention provides for the flow of petroleum vapors under controlledpressure conditions to a brine or glycol solution where the vapors arepassed directly into contact with such solution, the temperature rangeof which is controlled so as to condense the hydrocarbon vapors andallow the water therewith to go into solution while the air bubbles onthrough the solution for discharge to atmosphere. Thus, the hydrocarbonvapors are not only controlled to prevent air pollution if they escapedto the atmosphere, but they are also condensed and recovered .with areduced cost compared to the known prior art systems.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic illustration ofthe apparatus of this invention used for carrying out the method of thisinvention;

FIG. 2 is an enlarged sectional view of a portion of the apparatus ofFIG. 1 and further illustrating the method of this invention; and

FIG. 3 is a modified form of the apparatus of this invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Various petroleum products suchas gasoline and other petroleum products are conventionally stored inextremely large storage tanks which may be several hundred feet indiameter and of a height equivalent to a multiple story building Becauseof the size of such a storage tank, one of which is indicated with theletter S in FIG. 1, variations in the ambient temperature to which suchtanks are exposed create pressure varia-,

tions resulting in uncontrolled vapor emissions. The apparatus andmethod of this invention provide for almost complete recovery of thehydrocarbons in the petroleum vapors so as to control air pollutionwhich might otherwise result if such volatile petroleum emissions escapefrom the storage tanks into the atmosphere. As will be more fullyexplained, the upper portion of each storage tank S, or a plurality ofsuch tanks S, are connected through suitable means, which will bedescribed, to a treating assembly A (FIG. 1) in which the petroleumvapors together with any water and air therewith, are passed in directcontact with a brine or glycol solution which is within a controlledtemperature range. The hydrocarbons in the petroleum vapors arecondensed in such apparatus or assembly A, the water goes into thesolution with the brine solution and dilutes it to some extent and, anyair which was with the petroleum vapors passes out into the atmospherein substantially uncontaminated form. The hydrocarbons which arecondensed may also be recovered for their value.

Considering the invention more in detail, and particularly the formillustrated in FIGS. 1 and 2, the storage tank or tanks S having thepetroleum products therein is each preferably formed with a fixed roofor top 10 having a check valve 11 for permitting the flow of air intothe tank S but preventing. the escape of vapors or gases from the tankS. I

The upper portion of the tank S is connected by a pipe 12 through whichpetroleum vapors which are formed in the upper end of the storage tank Smay flow under certain conditions as hereinafter described. To preventthe roof or top 10 of each storage tank S from being subjected toexcessive forces which might cause distortion, bending or even collapsethereof, the pressure within the upper part of the storage tank S isdesirably maintained at a pressure close to atmospheric pressure orother pressure outside of the tank S. The provision of the check valve11 provides for the entry of air to equalize the pressure internally ofthe tank S with the atmospheric pressure in the event there is areduction of pressure in the upper portion of the storage tank S. If thepressure within the storage tank S exceeds example, the valve 14 may beoperated by a conventional pressure control device 15 which is connectedbetween the valve 14 and the upper end of the storage tank S so that thevalve 14 is opened when the pressure in the upper end of the storagetank S exceeds onefourth of an ounce above atmospheric pressure, and itremains operable so as to keep the valve 14 open until the pressuredrops below such pressure. Thus the apparatus of this invention insuresthat the pressure of the vapors in the upper end of the storage tank Sto which the apparatus is connected never exceeds the pressure which isset by the pressure control device 15 and that is set so as to preventany damage to the storage tank itself by reason of pressure changestherein.

A blower is connected to the line 12 through the valve 14 with a line19, such blower normally being of a type developing a fairly lowpressure of l0 pounds per square inch or less, but not actually servingas a compressor because of the dangers involved in the use of acompressor with petroleum vapors. The blower 20 is preferably operatingat all times and the flow therefrom is controlled by a valve 21 and alsopreferably by a valve 22, the location and functioning of which will bedescribed.

Thus, when the valve 14 is closed, the blower 20 circulates vapors orair through line 23, open valve 21, line 24 and back to line 19 tore-entry into the blower 20. The valve 22 is closed under suchcircumstances to prevent flow to the assembly A. The valve 22 is locatedin line 25 which also leads from the blower 20 so that when the valve 14is opened by the pressure control device IS, the pressure sensed in thetank S operates to open the valve 22 and the pressure sensed in line 19op-- erates to close the valve 21 so that the blower 20 then causes thepetroleum vapors to flow through the line 25 to the apparatus orassembly A.

As illustrated in particular in FIGS. 1 and 2, the assembly of apparatusA includes a tank or container which has a divider plate 30a therein fordividing the tank into two separate compartments, one of which has abrine or glycol solution B therein. Such solution B is preferably aglycol such as propylene glycol or ethylene glycol. An inorganic brinesuch as calcium cloride may also be utilized. The concentration of thesolution depends upon the particular concentration and type of thehydrocarbons in the petroleum vapors which are passed through thesolution, examples of which will be provided hereinafter.

The petroleum vapors which include any air and water therewith, areintroduced into the solution B through the inlet pipe 25 at the lowerend or bottom portion of the compartment of the tank 30 in which thesolution B is disposed. A conventional sieve tray 32 or similar means islocated near the bottom of the solution B, and the petroleum vapors aresparged into the solution B through the sieve tray 32 so that the vaporsbubble up through the cold solution B. The solution itself is keptat acontrolled temperature which is regulated so that the temperature is lowenough for maximum recovery of the hydrocarbons in the petroleum vapors.

The temperature of the solution B is thus variable but broadly it wouldbe within a range of about 20 F to about F. As'illustrated in FIGS. 1and 2, such temperature control is preferably provided by arefrigeration unit 33 of conventional construction which providesrefrigerant in a coil 34 disposed in the solution B. The upper level ofthe solution B is controlled by an overflow wier 35 which has a flowtube 36 therewith extending through the divider plate 300 so that theoverflow of the solution B flows into a decanter section C of the tank30 which is separate from the solution B. The decanter section Cprovides a quiet settling area to effect a liquid separation by gravityof the condensed hydrocarbons in an upper layer l-l floating on top ofthe separated solution B which is a weak solution compared to thesolution B because of the water dissolved therewith. A conventionalfloat 40 operably by the solution B only may be utilized in the decantersection B for maintaining the level of the weak solution B at apredetermined height. Thus, such float 40 may be connected to a controlvalve 41 in a discharge line 42 leading to a solution regeneration unit43 where the solution B is reconcentrated in the known manner so that itis at the same strength as the solution B. A pump 44 is utilized forpumping the regenerated solution from the regenerator 43 back throughline 45 into the solution B. A cascade pump 51 maintains a continuousflow from C to B through line 50, such flow being controlled so as toallow adequate decanting time in decanter section C. y

The condensed hydrocarbons H are decanted from the decanter section Cthrough an overflow pipe 46 which leads to a storage reservoirlnotshown). A vent opening or stack 50 is provided in the upper end of thetank 30 so that the air which has bubbled through the brine solution Bmay escape to the atmosphere. Since the majority of the hydrocarbons arecondensed in the solution B, the gas thus escaping through the opening50 is essentially all air, with a minimum of hydrocarbon vapors and thusair pollution is minimized or prevented.

ln carrying out the method of this invention, using the apparatus ofFIGS. 1 and 2, the petroleum vapors are passed from the stroage tank S,or a plurality of such tanks S, to the apparatus A. Thus, the petroleumvapors which include the hydrocarbons such as propane, butane, pentaneand heavier, together with any water or air are transmitted and arecaused to flow through the brine solution B. The contact of suchpetroleum vapors, including the water and air, is thus directly with thesolution B. This is important because if water is present with thepetroleum vpaors, which is almost always the case, the water willfreeze, as is the case in prior art systems; however, in this inventionit will not freeze since it goes into solution with the solution B;hence there is no interference with the condensation of thehydrocarbons, and it does not block off flow of the petroleum vapors orthe air therewith with the result so that in the absence of freezingthere is no danger of explosion of the apparatus or other adverseeffects.

For normal hydrocarbon recovery, the lowest practical temperature isabout -20 F for such solution B, although normally the operatingtemperature would be somewhat higher thanthat. By way of example, withpercent propylene glycol (by volume) as the solution, and with the other20 percent (by volume) being water, the temperature of the solution Bwould be maintained between about 10 F and about 15 F torecover aboutpercent of propane and heavier hydrocarbons which would be normallypresent in a gasoline storage tank having a gasoline blend storedtherein. When the solution B is an 80 percent ethlene glycol solution,with the other 20 percent being water, butane and heavier hydrocarbonsmay be condensed and recovered up to about 90 percent or better bymaintaining the solution B at a temperature as high as 40 F, butpreferably in the neighborhood of 30 F. Thus, it can be seen that thepercentage concentration of the glycol to water may be varied dependingupon the temperature level desired and also the particular hydrocarbonswhich are being condensed and recovered. Such factors may be readilydetermined by those skilled in the art, using the foregoing examples forguidance.

Because water is brought into the solution B with the petroleum vapors,the solution B is constantly being diluted and therefore when thesolution B has been separated from the condensed hydrocarbons H as seenin FIG. 2 the solution B is regenerated by heating same to boil off someof the water or by otherwise removing some of the water in any mannerknown to those skilled in the art. Make-up solution is also added asdesired to compensate for any of the solution which is lost in theprocess by vaporization or otherwise.

A modified form of the apparatus and the method of this invention isillustrated in FIG. 3, which is adapted to be used for individual tankcontrol. Thus, although the apparatus of FIGS. 1 and 2 may be connectedto multiple tanks S, the form of the invention shown in FIG. 3 isconstructed for connection to only a single tank 8-], a portion of whichis illustrated in FIG. 3 The contactor apparatus A-l of FIG. 3 isconnected through a control line 112 to the upper end of the storagetank S-l so that any petroleum vapors collected therein may flow intothe apparatus A-l. Such flow may be specifically regulated with avalve-14 and a pressure control device 15 such as illustrated in FIG. 1,or the vapors may pass through line 112 as the pressure develops in theupper end of the storage tank 8-1. When the pressure reaches apredetermined amount in the line 112, a pressure control device 115 isactuated to operate a valve 114 so that thereafter the brine from thetank 130 flows through the valve 114 and line 60 to spray heads 61 inthe apparatus A-l. Thus, the solution is sprayed into the unit A-l so asto directly contact the petroleum vapors together with any water or airtherewith. The water and the hydrocarbons are thus condensed by thespray of the solution from the spray nozzles 61 and they flow throughline 62 to a separator C-l. The separation in the separator C-l ispreferably by decanting in such manner as heretofore described inconnection with FIGS. 1 and 2. Thus, the hydrocarbons H-l are at theupper level and the weak solution B'-I is at the lower level. The levelis preferably maintained by a suitable float control 140 correspondingto the float control 40 of FIG. 2 which operates a control valve 141returning the brine solution to the brine tank 130. The condensedhydrocarbons H-l flow through line 63 to a storage tank 64 having anysuitable controls therewith. The solution is refrigerated using aconventional refrigeration apparatus 133 and a refrigeration coil 134 inthe solution so as to maintain the temperatures of the solution withinthe limits heretofore disclosed in FIGS. 1 and 2.

An excess flow valve 65 may be provded in line 60 from the tank 130 tocontrol the volume flow of the brine solution to the contactor apparatusA-l so as to prevent overflow at the contactor A-I. Also, a small bypassline 1 14a is provided around the valve 114 so that there is always asmall amount of flow to the contactor A-I to maintain a low temperaturetherein at all times.

It is to be noted that the alternate form of the invention shown in FIG.3 does not require a blower such as the blower 20 to bring the vapors tothe apparatus since the tank is pressurized with nitrogen or other gasin the upper portion 130a above the liquid level of the solution so asto provide sufficient pressure to move the solution to the contactor A-lwithout pumping.

Although the invention has been specifically described for recoveringvapors from petroleum storage tanks, it should be understood that thisinvention is not limited to such source for the petroleum vapors, sincethe petroleum vapors may come from any source.

The foregoing disclosure and description of the invention areillustrative and explanatory thereof, and various changes in the size,shape, and materials as well as in the details of the illustratedconstruction may be made without departing from the spirit of theinvention.

I claim: 1. A method of controlling volatile petroleum emissions from astorage tank, comprising the steps of:

transporting petroleum vapors together with any water and air therewithby a low pressure blower to a liquid bath having therein a solutionselected from the group consisting of brine and glycols; regulating thepressure of the petroleum vapors in the storage tank by admitting airinto the tank when the pressure drops below a predetermined amountrelated to atmospheric pressure, and by effecting said transporting ofthe petroleum vapors to the solution when the pressure in the tankexceeds a predetermined amount related to atmospheric pressure; bubblingsaid petroleum vapors together with any water and air therewith upwardlythrough and in direct contact with said solution in said bath;

- controlling the temperature of said solution so that it is low enoughto condense a substantial portion of the hydrocarbons in said vapors;

causing any water with said petroleum vapors to go into solution withsaid solution;

separating any air from said petroleum vapors by the discharge of theair from the upper surface of the liquid bath; and

separating said condensed hydrocarbons from said solution.

2. The method set forth in claim 1, wherein:

the temperature of the solution is controlled by refrigerating same.

3. The method set forth in claim 1, wherein:

the temperature of the solution is maintained within a range from aboutminus 20 F to about 40 F.

4. The method set forth in claim 1, wherein:

said condensed hydrocarbons are separated from the solution by decantingsaid condensed hydrocarbons.

5. The method set forth in claim 1, including:

regenerating the brine solution after it has been diluted with the waterintroduced with the petroleum vapors so as to maintain the strength ofthe solution at an adequate level for the condensation and recovery ofthe hydrocarbons therein.

6. The method set forth in claim 1, wherein:

said solution is a glycol.

7. Apparatus for controlling volatile petroleum emissions from a storagetank, comprising:

a storage tank;

means for effecting transporting of the petroleum va- 10 pors to thesolution when the pressure in the tank exceeds a predetermined amountrelated to atmospheric pressure;

means for supplying the solution;

means for bubbling said petroleum vapors together with any water and airtherewith upwardly through and in direct contact with said solution insaid bath for condensing a substantial portion of the hydrocarbons inthe petroleum vapors, allowing the water therewith to go into solutionwith the brine, and separating the air for discharge therefrom;

means for separating said condensed hydrocarbons from the brinesolution.

8. The apparatus set forth in claim 7, wherein said means for separatingsaid condensed hydrocarbons includes:

means for overflowing the solution and condensed hydrocarbons togetherinto a settling tank; and means for thereafter decanting thehydrocarbons from the solution in the settling tank.

v UNITED STATES PA ENT OFFICEV- CERTIFICATE OF CORRECTION Patent No.5,778,968 Dated December 18, 1973 InVentr( George Parker, Sr.

Itvis certified that error appears in the above-identified patent andthat said Letters Patent are hereby corrected as shown below:

On the cover page, after the name of the assignees,

delete Houston? and substitute therefor Corpus Christi Signed and sealedthis 3rd day of December 1974. V

(SEAL) Attest:

McCOY M. GIBSON JR. c. MARSHALL DANN Attesting Officer Commissioner ofPatents )RM PC1-1050 (10-69) USCOMM-DC-60376,-P69

9 U. 5; GOVERNMENT FRINY NG OF I'ICE l9, 0-3Ci-l8l.

2. The method set forth in claim 1, wherein: the temperature of thesolution is controlled by refrigerating same.
 3. The method set forth inclaim 1, wherein: the temperature of the solution is maintained within arange from about minus 20* F to about 40* F.
 4. The method set forth inclaim 1, wherein: said condensed hydrocarbons are separated from thesolution by decanting said condensed hydrocarbons.
 5. The method setforth in claim 1, including: regenerating the brine solution after ithas been diluted with the water introduced with the petroleum vapors soas to maintain the strength of the solution at an adequate level for thecondensation and recovery of the hydrocarbons therein.
 6. The method setforth in claim 1, wherein: said solution is a glycol.
 7. Apparatus forcontrolling volatile petroleum emissions from a storage tank,comprising: a storage tank; a low pressure blower means for transportingpetroleum vapors together with any water and air therewith from thestorage tank to a liquid bath having therein a solution selected fromthe group consisting of brine and glycols; means for regulating thepressure of the petroleum vapors in the storage tank by admitting airinto the tank when the pressure drops below a predetermined amountrelated to atmospheric pressure; means for effecting transporting of thepetroleum vapors to the solution when the pressure in the tank exceeds apredetermined amount related to atmospheric pressure; means forsupplying the solution; means for bubbling said petroleum vaporstogether with any water and air therewith upwardly through and in directcontact with said solution in said bath for condensing a substantialportion of the hydrocarbons in the petroleum vapors, allowing the watertherewith to go into solution with the brine, and separating the air fordischarge therefrom; means for separating said condensed hydrocarbonsfrom the brine solution.
 8. The apparatus set forth in claim 7, whereinsaid means for separating said condensed hydrocarbons includes: meansfor overflowing the solution and condensed hydrocarbons together into asettling tank; and means for thereafter decanting the hydrocarbons fromthe solution in the settling tank.